U.S. distributors and freight hauliers have held down diesel consumption even as their business recovers from recession by making thousands of small changes to their operations.

Improved driver training, restrictions on idling and careful route planning to reduce deadheads (where vehicles travel empty) are all reducing consumption of expensive diesel while helping companies promote their green credentials.

"In 2011, we achieved almost 69 percent improvement in fleet efficiency over our 2005 baseline," Wal-Mart boasted in its 2012 Global Responsibility Report. "We delivered 65 million more cases, while driving 28 million fewer miles, by increasing our pallets per trailer and better managing our routes."

"Our network efficiency improvement equates to avoiding nearly 41,000 metric tons of carbon dioxide emissions, the equivalent to taking 7,900 cars off the road," the company wrote.

In 2013, FedEx will have improved the fuel efficiency of its U.S vehicle fleet by 22 percent compared with 2005, Chairman Frederick Smith said at CERA Week. It has surpassed its previous goal of a 20 percent improvement by 2020 seven years early. Smith has now committed the company to an even more ambitious 30 percent target for the global vehicle fleet by the end of the decade.

Fuel conservation programs are being replicated at hundreds of firms across the transportation and logistics sector.

"The price of oil and fuel volatility is definitely a driver, but not as much as the push to reduce carbon emissions," according to a consultant from PricewaterhouseCoopers quoted in a special report published by the University of Pennsylvania's Wharton School ("Greening the supply chain: best practices and future trends" 2012).

In practice, what started as a carbon-saving program during the 2004-2008 boom has become a cost saving initiative in the lean years that have followed.

"Adding efficiency to any part of the supply chain produces better returns. The good thing is that much of what we do to improve fuel economy translates to the bottom line as improved profitability. Every bit of energy you save is money in your pocket," according to Wharton.

The overall impact of thousands of energy saving decisions has been enormous. The United States consumed 3.7 million barrels of distillate fuels a day on average in 2012, down almost 11 percent from a peak of 4.2 million barrels a day in 2008.

The drop in diesel consumption has been much sharper than for gasoline demand, which fell just 6 percent over the same period.

In contrast to private passenger vehicles, which mostly run on gasoline in the United States, diesel is mostly used in trucks and other commercial vehicles, and has borne the brunt of cost-cutting.

Single-unit and combination tractor-trailer trucks consumed 42 billion gallons (159 billion litres) of fuel and travelled 267 billion miles (430 billion km) in 2011, sharply down from 48 billion gallons and 311 billion miles in 2008, according to the Federal Highway Administration's annual statistics about road use.

Driver Behavior

Some of the simplest ways to save fuel involve changing driver behavior. Many firms in the Environmental Protection Agency's "Smartway" fuel saving program have banned engine idling at loading and unloading facilities, as well as truck stops along the road. Others have instructed drivers to reduce speeds (driving at 55 miles per hour uses up to 7 percent less fuel than at 65 miles per hour).

Another strategy is to replace the standard set up of two standard tires and wheels with a single wide-base tire (cutting fuel consumption around 3 percent). Ensuring tires are inflated to the correct pressure helps reduce drag from contact with the road surface.

In some instances, truck stops without climate control have been refitted with heating and airconditioning to stop drivers idling their trucks to stay warm or cool, according to the EPA.

Driver retraining has been backed up by engine-monitoring software which can detect fuel-wasting aggressive acceleration and v